(1) Field of the Invention
The present invention relates to a valve and a semiconductor fabricating equipment using the same, and particularly, to an actuator for opening and closing action in a valve adapted to control a flow rate of fluid, and a semiconductor fabricating equipment for forming a semiconducting film on the surface of a substrate by swiching different kinds of source gases using the above valve.
(2) Description of the Prior Art
There has been disclosed an actuator for a valve or the like used to control a flow rate of a trace of fluid, in Proceedings of the IEEE Micro ElectroMechanical System, pp 95-98, 1990, wherein the actuator comprises a sheet having one end being fixed to serve as a valve body and an electrode which has a passage port and is disposed on the lower side of the sheet surface whereby the sheet is displaced by an electrostatic force for opening and closing the passage port.
Specifically, the above actuator is constituted of a dielectric with a passage port including a plate electrode on a silicon substrate, and a valve body made of a dielectric including a plate electrode for opening and closing the passage port, wherein the sheet is attracted to the electrode surface by an electrostatic force generated between the electrodes, to thereby close the passage port provided on a part of structure on the electrode side. Meanwhile, the opening of the passage is effected by utilizing a restoring force of the sheet functioning as a spring. In the above actuator, it takes comparatively long time to open and close the passage port. Particularly, the time required for opening the passage port is restricted by the quickness of the returning of the sheet due to the restoring force thereof and is hence difficult to be made shortened. Also, the electrostatic force acted in closing the passage port must be too large to resist the restoring force of the sheet functioning as a spring. The electrostatic force is inversely propotional to the square of the distance between the electrodes. Accordingly, in order to obtain a sufficient electrostatic force to resist the above restoring force, the above-mentioned conventional structure needs to makes smaller the distance between the sheet and the electrode located under the sheet up to a gap, for example, of several ten .mu.m. Therefore, since a flow rate of fluid is restricted by the distance between the sheet and the electrode under the sheet, a valve using the conventional actuator has a difficulty to control a large flow rate of fluid.
The technique of forming a semiconducting film on a semiconductor substrate is an important process in the fabrication of semiconductor devices such as IC, and LSI. In general, the epitaxial growth process requires switching of plural kinds of gases. As shown in FIG. 23, the switching of gases in a semiconductor fabrication has been carried out with use of a valve 50 provided in a tube 51 connected with a gas bomb disposed separatedly from a vaccum chamber 49 internally including a substrate 48 (disclosed, for example, in Japanese Patent Laid-Open No. sho 63-136616).
In the above-mentioned Japanese Patent Laid-Open No. sho 63-136616, there has been proposed a system comprising an opening and closing equipment provided between an epitaxial growth chamber and a gas introducing vessel whereby gas is exhausted from the gas introducing vessel in closing the opening and closing equipment.
Recently, with micronizing semiconductor devices, the epitaxial growth technique is required to form an extremely thinned film, for example, a superstructure having a layer thickness of at least 1 nm with accuracy of atomic order. As shown in FIG. 23, the prior art includes a long pipe from a valve 50 to a vacuum chamber 49, which occurs a delay time between valve switching and gas-flow switching in the vacuum chamber, and which makes the change in gas pressure slow. Accordingly, for the purpose of forming a superstructure on a substrate by alternately introducing different kinds of gases within the vacuum chamber, the prior art has disadvantage of not sufficiently controlling the atomic arrangement of the superstructure and of taking a long period of time for film growth.
Furthermore, the above-mentioned prior art has a large disadvantage accompanied by supplying gas from the gas introducing vessel. For example, it has a difficulty to supply a reaction gas in a minimum amount required for epitaxial growth only in the vicinity of the surface of the substrate. This is due to the fact that there has been merely known such an opening and closing equipment as being in a grade of a shutter used in a Molecular Beam Epitaxy (MBE). Even in the above-mentioned Japanese Patent Laid-Open No. sho 63-136616, there has been not disclosed the more concrete form of the opening and closing equipment.
Meanwhile, for making the semiconductor fabrication speedy, there has been proposed a technique of disposing a nozzle in the vicinity of a substrate to be processed, and of mechanically controlling the port of the nozzle for opening and closing action. However, the technique is disadvantageous in that the mechanical opening and closing action tends to yield pulsating current of fluid, that is, turbulent flow in a gas passage, which is unsatisfactory for the fabrication of the above mentioned micro-superstructure or the like.